Yes, blood tests are somewhat useful, though negative blood tests do not prove a lack of allergy; in fact, many negative blood tests are false negatives. (For IgE allergies, skin tests tend to have more fewer false negatives.) However, if you're avoiding the skin test because of the reactions you've had, what you need is an epi-pen prescription more than a test of any sort. reactions are likely to get more serious not less so and nut allergies should across the board be considered life-threatening and warrant an epi-pen (NOT just Benadryl), whether or not your past reactions have been life-threatening. You cannot count on avoidance; I believe one study showed that most food-allergic people have an accidental exposure at least once every five years.
If you have documented reactions to touching or ingesting peanuts (or treenuts), you need to see a good allergist (one who treats patients with food allergies, not just patients with respitory allergies) ASAP, and you need that prescription to keep you and the baby safe.
You also need to start avoiding all nuts, not just peanuts, as virtually all nuts are likely to be processed on equipment that's cross-contaminated with peanuts.
If you can't get a referral to an allergist quickly, then ask your regular dr or OB to prescribe epis for you preventatively while you wait for your allergist appointment. You need to have at least two (in case one malfunctions or gets left in the hot car, etc) with you at all times, as well as Benadryl. But Benadryl on its own is not enough if you go into anaphylaxis.
You may also want to join the forums at kidswithfoodallergies.org; your baby will be considered at high risk for allergies and the forums there have lots of good advice on how to breastfeed an potentially allergic infant, how to manage a reduced diet due to allergies during PG, etc. The main forum membership is free; subforums and the recipe database are subscription-only but the fee is small and can be waived (subsidized memberships) if you need it.
